Demonstrators heckled San Francisco Mayor Ed Lee off the stage Monday during Martin Luther King, Jr. Day ceremonies. They demand that the mayor fire his police chief -- the same demand they've made since the Mario Woods shooting early last month.

Mario's mother, Gwen Woods, said, "I'm sure I speak for every mother who lost their baby. I wonder how scared he was..."

Gwen appeared with her attorney John Burris, who announced that they had formally asked the U.S. Department of Justice to investigate the officer-involved shooting of her 26-year-old son. Burris said Lee had made the wrong decision to ask the San Francisco Police Department to conduct the investigation.

"He should not have appointed Chief Greg Suhr to do the evaluation. This is very much like the fox protecting the chicken house," Burris said.

Woods died in a barrage of gunfire last month in San Francisco's Bayview District. All of it was caught on camera. Police say video shows him raising his hand with a knife toward one of the five officers. Burris says another video shows Woods' hand going up after he was shot, with no knife in sight.